The present invention relates generally to the field of electric motors, and more particularly, is directed to a low profile direct current electric motor which may be used in restricted space areas.
Low profile or so-called "pancake" motors are used in a wide variety of applications. Many of these applications demand a motor that is both small in size and is capable of delivering high output torque. For example, such motors are often installed in the door panels of automobiles for operating a power window system. In modern automobiles, however, door panels are becoming increasingly thinner. Thus, any devices installed in the door panel must be correspondingly thinner. Low profile motors known in the prior art that were at one time suitable for this application are fast becoming fewer in number.
One embodiment of a conventional low profile or pancake motor comprises a disk-shaped armature having so-called printed circuits. The printed circuits form a winding with a limited number of turns. Because the number of turns in each winding is limited, the magnetic flux generated by the windings is correspondingly low. Thus, the output torque of the motor is very small. Moreover, the limited number of turns in the windings result in a motor having a very low impedence. Thus, such motors are suitable only for low voltage operation. The armature of the motor also includes a hole for the motor shaft. Such a hole reduces the flux area of the armature and thus the available torque of the motor.
U.S. Pat. No. 3,315,106 issued in the name of Reynst discloses a pancake motor design which addresses some of the deficiencies in pancake motors known in the prior art. The Reynst motor comprises an armature having windings with a relatively large number of turns. The windings are wound through slots in the armature to increase the number of turns in each winding. Thus, the motor can produce more torque than motors known in the prior art. In the manufacture of such a motor, however, substantial time and care is required in placing the windings in the slots. Thus, mass production of motors of this design is not economical. Moreover, the armature has a relatively large hole for the motor shaft, thus reducing the flux area of the armature and its available torque.